Safety AdvisorSafety Advisor

Fighting FatigueFighting Fatigue

Fatigue affects our ability to fly. For example, it can impair memory, judgment, concentration, vision, and coordination. An overwhelming desire to sleep is the most pronounced symptom of fatigue. This Safety Advisor examines factors leading to fatigue and how to keep it from catching up with you in the cockpit.

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Section 1: Sleep Deprivation

The most obvious cause of fatigue is a lack of sleep. Different people need different amounts of sleep, but for most adults the critical amount is between seven and eight hours a night. If you’re regularly deprived of a good night’s sleep, it will eventually catch up with you. For example, it may affect your ability to concentrate, and you may become overwhelmed by a desire to sleep. The best defense against fatigue is to change your sleeping pattern and get a full night’s rest on a consistent basis: One good night of sleep won’t make up for days of sleep deficit.

Avoid flights that arrive after 10 p.m. If that’s not possible, try to get plenty of preemptive rest and consider bringing another pilot along.

Body Clock

The human body has an internal clock, a “circadian rhythm” set by external cues (primarily daylight and darkness: See Section 3: Circadian Rhythm). It’s the reason we’re generally sleepy at night and active during the day. It’s not difficult to throw your clock out of sync. A fast, long-range aircraft can easily cross several time zones in a single flight, disrupting the pilot’s circadian rhythm and causing a condition known as jet lag.

But jet lag isn’t the only way to end up at cross-purposes with your body’s clock. For general aviation pilots, end-of- the-day flights are more often the problem.

Scenario Business Trip

You depart in the early-morning, fly several hours, spend the day in a meeting, and then fly home the same evening. That may not sound so bad—but take a closer look. It can be difficult to sleep the night before an important trip. Preparing for a cross-country flight can be stressful, particularly if the weather is marginal and it’s important to get to the destination. There may be delays because the airplane has mechanical problems or weather leads to ATC reroutes. That’s just getting to the meeting, which may itself involve conflict and difficult decisions. By the time the meeting is finished, you’ll have been awake for more than 12 stressful hours (a good portion of which was spent at altitude). Yet you plan to fly single-pilot IFR, at night, in a high-performance airplane—at a time when your body naturally wants to “call it a day.” It’s a situation that easily demands more of you than you physically or mentally can give.

Scenario Family Travel

Many of the same issues that crop up on business trips—passenger expectations and pressure to get home before a certain time—also cause trouble flying cross-country for the holidays, or taking the airplane on vacation. The circumstances are very different, but the factors that lead to fatigue are much the same.

Take it Easy

The best advice is to stick to as normal a schedule as possible. Don’t put yourself in “need to get home” situations. If you know it’s going to be a long day, plan to spend the night and depart the following morning. Avoid flights that arrive after 10 p.m. If that’s not possible, try to get plenty of preemptive rest and consider bringing another pilot along. If you feel any serious concern about your level of fatigue, stay on the ground.

Feeling Drowsy

“My mind clicks on and off…I try letting one eyelid close at a time while I prop the other open with my will. But the effort’s too much. Sleep is winning. My whole body argues dully that nothing, nothing life can attain, is quite so desirable as sleep.”

Wake Up!

The private pilot had gone to bed at 2 a.m. and although the alarm went off at 4 a.m., he slept until about 7:30 a.m. During the morning and early afternoon, he attended college classes and took a test. Using the college’s commercial/instrument rating curriculum, the pilot had planned a night cross-country flight with landings at three different airports, including one 250-nautical mile leg between two of the airports. At 6:15 p.m., he departed Grand Forks (GFK), North Dakota, flew to Airlake Airport (LVN) and then to Crystal Airport (MIC) in Minnesota, where he refueled the airplane and met with a friend for a meal before returning to GFK. The pilot remembered departing MIC at 11:55 p.m., climbing to 4,500 feet msl, opening his flight plan with flight service, and flying for about 1.5 hours on a northwesterly heading. He saw the Detroit Lakes in Minnesota in the distance, but that was the last thing he remembered. When he opened his eyes, the airplane had crashed in a cornfield. The pilot told the NTSB, “First, I should not have taken off thinking that I might get tired. I should have requested flight following to keep my attention. Possibly, I should have recognized symptoms of fatigue and state of consciousness, and landed before losing consciousness.”

Power Naps

If you’re feeling drowsy, a short nap of 15 or 20 minutes can be a very effective way to regain alertness and decision-making ability. It’s generally best to keep naps short to avoid entering the deep part of the sleep cycle. Longer naps often lead to more severe “sleep inertia”—that groggy, drowsy feeling after you wake up.

Did You Know?

A study published in Nature magazine showed that people who stay awake for 17 hours straight function at a level similar to those with a blood-alcohol content of 0.05 percent—beyond the legal limit for flying.

Section 2: Sleep Sense

Consistent, uninterrupted, adequate sleep allows the body to rest and recover. But extensive traveling, consuming excessive alcohol and caffeine, or staying up late can wreak havoc on our sleep pattern. In addition, aging and various medical conditions—such as depression, stress, sleep apnea, etc.—can influence how well we sleep.

Dozing Off

The Cessna 150 was substantially damaged when it struck a snow bank during final approach. According to the certificated flight instructor, he and his student were flying a normal approach. On a half-mile final the student pilot extended the flaps to 40 degrees. At this point the CFI “fell asleep for 20 to 25 seconds.” He opened his eyes just before the wheels hit the snow bank but did not have enough time to react and prevent the impact. The airplane’s nose landing gear collapsed and the airplane slid to a stop. Neither the student nor the CFI were injured. The CFI said he had been unable to stay awake due to lack of sleep the night before.

Beyond a Yawn

We know the obvious “red flags” (yawning, heavy eyelids), but it’s important to stay alert to more subtle signs as well. Some people notice a ringing in their ears, while others have difficulty with tasks that require dexterity or coordination. Fatigue can also lead to noticeable cognitive and behavioral changes. Many people find themselves feeling irritable, losing focus in the middle of extended tasks (checklists, for example), or having trouble making relatively simple decisions.

Snooze Alert

Although a lack of sleep is normally the underlying cause of fatigue, other factors can trigger how tired we feel. Here are some common reasons and suggestions for dealing with them:

Medical Self-Assessment: Stress

This video excerpt from No Greater Burden: Surviving an Aircraft Accidentis featured in the Medical Self-Assessment: A Pilot’s Guide to Flying Healthy online course. Explore how stress, emotion, and fatigue can impact concentration.

Section 3: Circadian Rhythm

To help minimize CRD after crossing time zones, try to reset your biological clock by getting out in the sun and daylight, staying active, and fitting in with the local eating and sleeping schedule.

Like Clockwork

Our brain relies on cues to regulate our wake/sleep schedules. For example, when daylight hits our eyes, cells in the retinas signal our brain that it’s time to wake up. Temperature, night time, sleep, physical activity, etc. are all cues to keep our circadian rhythm in sync. However, as a natural part of aging we’ll experience changes in our sleep pattern such as earlier onset of sleepiness, early-morning awakenings, and an increased need for daytime napping.

Combat Jet Lag

Adjust bedtime by an hour a day a few days before the flight to match the sleep schedule at your destination.

Reset your watch at the beginning of the flight to adjust more quickly to the new time zone.

Drink plenty of water before, during, and after the flight.

Eat lightly but strategicallyas it influences your wake/sleep cycle. High-protein food can keep you awake, while foods high in carbohydrates can promote sleep, and fatty foods may make you feel sluggish.

Getting Out of Sync

When the circadian rhythm is altered or interrupted, it affects our physiology and behavior.

Several chronic sleep disorders can lead to circadian rhythm disruptions (CRD):

Delayed Sleep Phase Syndrome. Causes late-evening insomnia, excessive early-morning sleepiness, difficulty falling asleep before 2:00 a.m., short sleep periods during the week, and prolonged sleep periods during the weekend. It is linked to depression and other psychiatric disorders.

Advanced Sleep Phase Syndrome. Causes early evening sleepiness and morning awakening, such as the urge to sleep between 6:00 p.m. and 8:00 p.m. and waking up between 1:00 a.m. and 3:00 a.m.

Non 24-Hour Sleep-Wake Disorder. Results from an inadvertent sleep delay, followed by unsuccessful attempts to sleep on schedule. Regular sleep delays interfere with circadian rhythms and result in a free-running “biological clock” of 25 hours instead of 24, causing inconsistent insomnia that affects the sleep cycle: sometimes the person falls asleep later and wakes up later; other times he or she falls asleep earlier and wakes up earlier.

CRD and Flying

Ignored CRD-induced fatigue affects your health and safety-of-flight. For example, you may experience increased time to react, decreased attention to tasks, impaired memory and tendency to forget secondary tasks, increased distraction, and emotional irritability. To help minimize CRD after crossing time zones, try to reset your biological clock by getting out in the sun and daylight, staying active, and fitting in with the local eating and sleeping schedule. Consult a physician to diagnose and treat persisting sleep problems. Learn more in the FAA’s Medical Facts for Pilots: Circadian Rhythm Disruption and Flying publication (AM-400-09/3).

Medical Self-Assessment: Fatigue

In this video from the Medical Self-Assessment: A Pilot’s Guide to Flying Healthy online course, discover how sleep environment, work shift, medical conditions, jet lag, and other factors can affect fatigue.

Section 4: Obstructive Sleep Apnea

Narrowing of the respiratory passages causes obstructive sleep apnea (OSA)—a repetitive upper airway obstruction during sleep. OSA is often associated with people who are overweight, have higher deposits of fatty tissue in their respiratory passages, and have larger then average size soft palates and tongues. These conditions decrease the size of the upper airway and decrease airway muscle tone. When a person sleeps on his or her back in a horizontal position, gravity can pull tissue down and over the airway, impeding air flow to the lungs during inhalation. This can cause snoring and a struggle to breathe.

Sleep Struggles

Someone affected by OSA may not realize it, even if snoring and struggled breathing interrupts his or her sleep many times at night. Loud and excessive snoring are usually the first signs of OSA. Other symptoms include:

Having trouble concentrating, thinking, or remembering

Being sleepy during the day

Feeling fatigued

Needing to take frequent naps

Having headaches

Being irritable

Having a short attention span

Breath In…Breath Out

When you stop breathing in your sleep, your brain automatically jumps into action and sends a wakeup call after about 10 seconds to prevent prolonged oxygen starvation. However, time zone changes and alcohol consumption can delay the triggering mechanism by 30 seconds or longer. Such oxygen starvation results in significant fatigue. In addition, repetitive decreases in blood oxygen levels can lead to chronic health problems.

Asleep at the controls

On a daytime flight in 2008, a commercial aircraft with three crewmembers and 40 passengers flew past its destination airport after both the captain and first officer fell asleep.
The pilot awoke and turned back to the destination airport, where all deplaned safely—but behind schedule. The National Transportation Safety Board (NTSB) determined that contributing factors to the incident were the captain’s undiagnosed obstructive sleep apnea (OSA) and the flight crew’s recent work schedules, which included several days of early-morning start times.
Learn more about the impact and treatment of OSA in the FAA’s Obstructive Sleep Apnea publication (AM-400-10/2).

OSA Induced Chronic Health Issues

Apnea-Hypopnea Index (AHI)

Apnea and hypopnea are defined as “total” and “partial” obstructions of the airway. Mild OSA is defined as an AHI of five to 15 apnea or hypopnea events per hour, severe OSA as an AHI of more than 30 events per hour, and moderate OSA falls between these ranges.

Are You Tipsy?

Most pilots will not fly intoxicated, but OSA sleep deprivation may cause the equivalent effect. Time zone changes and post-flight alcohol consumption further exacerbate the condition.

OSA Treatment Strategies:

Consult your doctor—OSA can be diagnosed through a sleep study and treatment is very effective.

Change sleeping routines—Adjust sleeping position from your back to your side or stomach.

Dental appliances—Dentists specialized in sleep medicine (American Academy of Dental Sleep Medicine) are trained in the use of oral appliance therapy for the treatment of obstructive sleep apnea and snoring.

Continuous positive airway pressure (CPAP) machine—Reduces AHI when used consistently six hours or more a night.

Surgical methods—These types of surgeries can be very significant, may not always succeed, and can lead to side effects. So try non-surgical methods first.

OSA can be diagnosed through a sleep study and treatment is very effective.

Section 5: Rules to Live By

The key to recognizing and combating fatigue is self-assessment—knowing your personal signs of fatigue, actively looking out for them, and making safe decisions. If you start noticing physical or mental issues, don’t just continue with business as usual. If you’re on the ground, it’s probably wise to stay there. If you’re airborne, do what you can to remain alert and consider diverting to a nearby airport. And if you’re already starting to nod off, it’s simple: Get the airplane on the ground as soon as practical.